1. Field of the Invention
Aspects of the present invention relate to a device and method to play back contents according to a reception sensitivity, and more particularly, to a device and method to select a wireless communication system according to the reception sensitivity of wireless signals, such as AirTV signals, digital multimedia broadcasting signals, or wireless LAN signals, and to play back received multimedia content.
2. Description of the Related Art
With the evolution of communication and network techniques in recent years, wired network environments using a wire medium, such as a coaxial cable or an optical cable, have become increasingly replaced by wireless network environments using radio waves in various frequency bands.
FIG. 1 shows multimedia content provided by conventional wireless communication techniques. In order to share communication paths, a wireless LAN 14 uses, for example, the IEEE 802.11 communication standard, the IEEE 802.11a communication standard, the IEEE 802.11b communication standard, or the IEEE 802.11g communication standard. These standards are wireless network standards using CSMA/CA (carrier sense multiple access/collision avoidance) (i.e., an Ethernet protocol) to transmit data at a transfer rate of 11 Mbps to 54 Mbps.
In addition to wireless LANs based on the IEEE 802.11 communication standard, wireless networks based on the IEEE 802.16e communication standard have been developed. This standard is called a wireless broadband 15. The wireless broadband 15 is an Internet service that uses a frequency bandwidth of 2.3 GHz and has a mobility of 60 km/h or more and a transfer rate of approximately 1 Mbps. The wireless broadband 15 has a maximum radio propagation distance of about 48 km, which is ten or more times larger than the service radius of the wireless LAN 14 that can be used in a service area called a hot-spot.
A user that wants to use a wireless network may access a local area network through a mobile network 11. In the wireless network using the mobile network 11, a base station relays between a wireless section and a wired section, which has an advantage in that a user in the mobile network 11 can use the wireless network.
A wireless technique to provide multimedia content can be applied to a satellite communication technique, which makes it possible for a user to view multimedia content transmitted from a satellite through a portable terminal 10. An AirTV system 12 and a digital multimedia broadcasting (hereinafter, referred to as DMB) system 13 may be used to display the multimedia content transmitted from the satellite.
The DMB systems 13 are classified into a terrestrial DMB system and a satellite DMB system according to a transfer means (a ground wave or a satellite, respectively). The terrestrial DMB systems are divided into an in-band type using an AM/FM band and an out-of-band type using a new frequency band. The in-band type has a bit rate of approximately 384 kbps, and the out-of-band type has a bit rate of approximately 526 kbps. The satellite DMB system provides a service in a frequency band of 2.535 to 2.655 GHz, which is an ultrahigh frequency considerably higher than the frequency band of the terrestrial DMB system. The terrestrial DMB system provides a service by using a transmitting station radiating radio waves, while the satellite DMB system provides a service by using a satellite outside of the earth's atmosphere. Therefore, the satellite DMB system can provide a service covering a wider range.
Although the AirTV system 12 has not yet been commercially used, the AirTV system 12 is expected to eventually provide approximately 60 TV channels with various languages, and Internet, e-mail, and data services at a transfer rate of approximately 40 Mbps.
As described above, wireless communication services can be provided through various wireless communication techniques. However, there are many wireless communication restrictions, such as a bandwidth restriction and an interference of radio waves, in providing services by using the various wireless communication techniques. That is, the portable terminal 10 may not smoothly receive multimedia content due to the surrounding environment and the communication environments. Therefore, in order to smoothly receive multimedia content, the user of the portable terminal 10 must move to a region where multimedia content is received at high reception sensitivity, or the user must receive the multimedia content only during a time period when the multimedia content is received at high reception sensitivity. The user of the portable terminal 10 provided with various wireless communication techniques should connect with a wireless communication system having a higher reception signal to receive multimedia content with a high reception sensitivity.
Korea Patent Unexamined Publication No. 2003-37373 discloses a method of realizing a roaming service that enables roaming between a wireless LAN and a mobile network and which detects the levels of reception signals received through a wireless LAN and a mobile network, compares the levels of the reception signals, and performs data communication through one of the wireless LAN and the mobile network having a higher signal level. However, in the above-mentioned method, comparison the levels of the received reception signals depends on the communication systems. This results in frequent switching between communication systems due to a variation in the surrounding environments, such as whenever the user moves from one place to another place. Therefore, there needs to be a method of stably receiving wireless communication signals without increasing the number of switching operations between communication systems.